Simple Chain Tensioner.

They say 'necessity is the mother of invention'. We have a small screening plant that was built out of scrap, in a hurry to fullfill a particular need. Another contractor needed a small screen to screen gypsum and we needed one to screen soil, so we knocked it up in a hurry a few years ago and it is still working and what's more it is doing the job very well. However, the chain drive that drives the conveyor under the feed hopper was giving me the ****'s, so I made one of these little fellers and it totally eliminated the problem. It is very easy to make, two pieces of flat steel, two bolts and two pieces of mallee, (a small, very hard wood, Australian Eucalypt), the modern version uses hard wearing nylon. The first photo also shows how the chain wears grooves in the wood until the rollers touch the wood and they just roll around it. It is very hard to keep constant tension on a heay drive roller chain, but this is self compensating, as the chain loosens, it slides a little further down, keeping a constant tension on the chain. It's a bit rough, but it works. This shows it in action. http://www.youtube.com/watch?v=bczx3P-A3jI RnR.